WASHINGTON – Russia’s war in Ukraine must end before the latter can join NATO, President Biden said Sunday — before heading across the pond to speak about the ongoing conflict and the environment with UK Prime Minister Rishi Sunak and King Charles III.

Biden, who left his Rehoboth Beach, Del. home for London on Sunday, is set to attend the NATO summit later this week in Lithuania — during which leaders of the allied nations are expected to discuss the potential of accepting Ukraine into the Western alliance.

The president told CNN ahead of his trip that he does not believe Ukraine should join the organization until the Russian invasion is over.

“I don’t think there is unanimity in NATO about whether or not to bring Ukraine into the NATO family now, at this moment, in the middle of a war,” Biden said.

“For example, if you did that, then, you know – and I mean what I say – we’re determined to commit every inch of territory that is NATO territory,” he continued. “It’s a commitment that we’ve all made no matter what. If the war is going on, then we’re all in war. We’re at war with Russia, if that were the case.”

Prior to the NATO summit on Tuesday and Wednesday, the president will visit with UK leaders on Monday, including meeting with Sunak at 10 Downing St. “to consult of a range of bilateral and global issues,” White House Press Secretary Karine Jean-Pierre said Friday.

Those issues are believed to include the nation’s ongoing support for Ukraine, as the nations are among the strongest supporters of Kyiv in the West.

Though the US has spent the most money supporting Ukraine – more than $40 billion in weapons alone – the UK has recently taken on a greater leadership role in the effort.

The UK has been supportive of international efforts to supply Ukraine with American-made F-16 fighter jets, nudging their US partners to green-light pilot training and more.

However, Biden may face awkward conversations with Sunak regarding the president’s Friday decision to send highly lethal – and controversial – cluster munitions to Ukraine.

The prime minister as recently as Saturday said that the UK “discourages their use.”

Next, Biden will visit King Charles at Windsor Castle to “engage with a forum that will focus on mobilizing climate finance – especially bringing private finance off the sidelines – for clean energy deployment and adaptation in developing countries,” Jean-Pierre said Friday.

It will be the first time Biden has met with the king since he was coronated in May. Biden skipped the pomp-and-circumstance ceremony, sending First Lady Jill Biden and one of their granddaughters in his place.

Russian President Vladimir Putin has used Ukraine’s bid to join NATO as one of his reasons for launching his invasion of the neighboring country Feb. 24, 2022.

It has been 15 years since NATO leaders in 2008 said Ukraine could eventually become a member, but the alliance has stayed largely mum on the topic in the years since, as the accession of the country that shares so much of its northern, eastern and southeastern border with Russia.

Ukraine President Volodymyr Zelensky remains committed to the cause of joining NATO, refusing to cower to Putin’s demands that Kyiv abandon all efforts to join the security alliance.

“I think we have to lay out a rational path for Ukraine to be able to qualify to be able to get into NATO,” Biden told CNN on Sunday.

“But I think it’s premature to say, to call for a vote, you know, in now, because there’s other qualifications that need to be met, including democratization and some of those issues.”